Halt Urged in Buying Sprays That Might Hurt Ozone

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An immediate halt to the purchase of spray cans using a propellant that some scientists fear may threaten the earth's protective ozone layer was recommended yesterday by the chairman of a committee appointed to assess the alleged threat.

The recommendation was made to the public by Dr. Donald M. Hunten of the Kitt Peak National Observatory in Tucson, Ariz. The committee he heads was formed by the National Academy of Sciences and held its first meeting in Washington on Saturday.

Dr. Hunten said he was speaking personally and not on behalf of the committee. While he declined to detail the conclusions reached at Saturday's meeting, he said: “The best opinion is that a problem is well on its way.”

Use Rising Rapidly

At a news conference in Tucson he said that, in view of the situation's urgency, he hoped the committee could complete its assessment within a year. Worldwide use of the propellants has risen rapidly, he added, with half a million tons being produced annually, at least half that total being made in this country.

He said it was futile to refrain from using spray cans already purchased because the gas inside would eventually enter the atmosphere, no matter how they were disposed of. The gases in question are chlorofiuoromethanes — known more broadly as fluorocarbons.

The current cause for alarm has been the report of evidence that, while these gases are normally inert, they break down under the glare of ultraviolet light, releasing chlorine that then breaks down ozone. Molecules of ozone are formed of three oxygen atoms, whereas ordinary oxygen molecules contain only two.

Some Damage Seen

Ozone in the lower stratosphere absorbs those wave lengths of ultraviolet light that are lethal to living things, making the earth habitable. Dr. Hunten said that if calculations by Dr. Michael B. McElroy of Harvard University were correct, continued use of the sprays could increase the incidence of skin cancer by 10 per cent or more and might affect crops throughout the world.

The calculations suggest, he said, that there is already enough of the propellant in the atmosphere to reduce the ozone layer by 1 per cent, causing a rise in skin cancer estimated at 1 per cent. However, he added, in view of year‐to‐year fluctuations that occur naturally in the ozone layer, the effect might not become indisputable until the depletion is 10 per cent.

Because of a lag effect there would then be enough of the gas in the air to reduce the layer by 15 or 20 per cent with a likelihood of disastrous effects. The manufacture of these gases, the best known of which, made by du Pont de Nemours & Co., is called Freon, has grown Co., is called Freon, has grown to such a large industry, Dr. Hunten said, that an immediate conversion to more; innocuous propellants was not practical.

Some substitutes are in use, but the fluorcarbons; are favored because, being inert chemically they do not react with whatever is being sprayed— paint, shoe polish and several hundred other products.

Stations around the world monitor the amount of ozone overhead by measuring the extent to which ultraviolet light from the sun is absorbed at the wave lengths where ozone is active. A study of such records from the northern hemisphere has been made by Dr. Julius London of the University of Colorado in Boulder and Jean I. Kelley of the National Center for Atmospheric Research, also in Boulder.

From August, 1957, until March, 1961, they recorded an annual decrease of 0.47 per cent. Then, until May of 1970, there vies an increase of 1.13 per cent annually. Data from the more recent period when spray cans proliferated have not yet been analyzed.” Readings from 160 worldwide stations for the period through 1972 have been received, Miss Kelley said yesterday, and are under study. She suspects that the increase observed through 1970 was a cyclic phenomenon that probably reversed in about 1973.

Dr. Hunten said measurements in remote regions had shown that the propellant gases were uniformly distributed around the world. Aircraft sampling in the lower, stratosphere showed it was there too, he added, although to a somewhat depleted extent. He found this an ominous hint that the gases were being broken down by the ultraviolet there.

One reason for concern is the predicted persistence of chlorine in th lower stratosphere, some 100,000 feet aloft, once it has been released there. Estimates for its persistence range from 50 to 100 years. Such predictionn, Dr. Hunten said, “do hava to taken seriously.